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Background Chlamydia trachomatis causes pelvic inflammatory disease (PID) and tubal infertility. Plasmid gene protein 3 antibody (Pgp3Ab) detects prior chlamydial infections. We evaluated for an association of high chlamydial seropositivity with sequelae using a Pgp3Ab multiplex bead array (Pgp3AbMBA). Methods We performed chlamydia Pgp3AbMBA on sera from women 18-39 years old participating in the 2013–2016 National Health and Nutrition Examination Survey (NHANES) with urine chlamydia nucleic acid amplification test results. High chlamydial seropositivity was defined as a median fluorescence intensity (MFI ≥ 50 000; low-positive was MFI > 551–<50 000. Weighted US population high-positive, low-positive, and negative Pgp3Ab chlamydia seroprevalence and 95% confidence intervals (CI) were compared for women with chlamydial infection, self-reported PID, and infertility. Results Of 2339 women aged 18–39 years, 1725 (73.7%) had sera, and 1425 were sexually experienced. Overall, 104 women had high positive Pgp3Ab (5.4% [95% CI 4.0–7.0] of US women); 407 had lowpositive Pgp3Ab (25.1% [95% CI 21.5–29.0]), and 914 had negative Pgp3Ab (69.5% [95% CI 65.5–73.4]). Among women with high Pgp3Ab, infertility prevalence was 2.0 (95% CI 1.1–3.7) times higher than among Pgp3Ab-negative women (19.6% [95% CI 10.5–31.7] versus 9.9% [95% CI 7.7–12.4]). For women with low Pgp3Ab, PID prevalence was 7.9% (95% CI 4.6–12.6) compared to 2.3% (95% CI 1.4–3.6) in negative Pgp3Ab. Conclusions High chlamydial Pgp3Ab seropositivity was associated with infertility although small sample size limited evaluation of an association of high seropositivity with PID. In infertile women, Pgp3Ab may be a marker of prior chlamydial infection. [ABSTRACT FROM AUTHOR]